title: Counteraction by nitric oxide synthase inhibitor of neurochemical alterations of dopaminergic system in 6-OHDA-lesioned rats under L-DOPA treatment.
abstract: Nitric oxide synthase inhibitors reduce L-3, (Del-Bel et al., Cell Mol Neurobiol 25(2):371-392, 2005) 4-dihydroxyphenylalanine (L-DOPA)-induced abnormal motor effects subsequent to depletion of dopaminergic neurons in rodents and non-human primates. The present study used quantitative high-performance liquid chromatography to analyze, for the first time, dopamine metabolism in striatum of rats in order to elucidate the mechanism of action of the nitric oxide synthase inhibitors. Adult male Wistar rats received unilateral microinjection of saline (sham) or 6-hydroxydopamine (6-OHDA-lesioned) in the medial forebrain bundle. Past 3 weeks, rats were treated during 21 days with L-DOPA/benserazide (30 mg/kg/7.5 mg/kg, respectively, daily). On the 22nd day rats received an intraperitoneal (i.p.) injection of either vehicle or 7-nitroindazole, a preferential neuronal nitric oxide synthase inhibitor before L-DOPA. Abnormal involuntary movements and rotarod test were assessed as behavioral correlate of motor responses. Lesion intensity was evaluated through tyrosine hydroxylase immunohystochemical reaction. Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and an extent of dopamine striatal tissue levels/dopamine metabolism were measured in the striatum. Lesion with 6-OHDA decreased dopamine, DOPAC, and DOPAC/dopamine ratio in the lesioned striatum. L-DOPA treatment induced abnormal involuntary movements and increased DOPAC/dopamine ratio (nearly five times) in the lesioned striatum. L-DOPA-induced dyskinesia was mitigated by 7-nitroindazole, which also decreased dopamine turnover, dopamine and DOPAC levels. Our results revealed an almost two times increase in dopamine content in the non-lesioned striatum of 6-OHDA-lesioned rats. Reduction of striatal DOPAC/dopamine ratio in dyskinetic rats may suggest an increase in the dopamine availability. Our data confirm contribution of nitrergic transmission in the pathogenesis of L-DOPA-induced dyskinesia with potential utilization of nitric oxide synthase inhibitors for treatment.
authors.affiliation: Department of Morphology, Physiology and Pathology, School of Odontology, University of São Paulo, Campus Ribeirão Preto, Av. Café S/N, Ribeirão Preto, SP, 14040-904, Brazil, eadelbel@forp.usp.br.
authors.forename: Elaine
authors.initials: E
authors.lastname: Del-Bel
authors.forename: Fernando Eduardo
authors.initials: FE
authors.lastname: Padovan-Neto
authors.forename: Raphael Escorsim
authors.initials: RE
authors.lastname: Szawka
authors.forename: Célia Aparecida
authors.initials: CA
authors.lastname: da-Silva
authors.forename: Rita
authors.initials: R
authors.lastname: Raisman-Vozari
authors.forename: Janete
authors.initials: J
authors.lastname: Anselmo-Franci
authors.forename: Angélica Caroline
authors.initials: AC
authors.lastname: Romano-Dutra
authors.forename: Francisco Silveira
authors.initials: FS
authors.lastname: Guimaraes
mesh_terms: D000818:Animals; D000978:Antiparkinson Agents / Q000633:toxicity; D003342:Corpus Striatum / Q000737:chemistry* / Q000187:drug effects; D004298:Dopamine / Q000032:analysis*; D004409:Dyskinesia, Drug-Induced / Q000188:drug therapy*; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D007191:Indazoles / Q000627:therapeutic use*; D007980:Levodopa / Q000633:toxicity; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D016627:Oxidopamine; D051381:Rats; D017208:Rats, Wistar; D013378:Substantia Nigra / Q000737:chemistry* / Q000187:drug effects / Q000473:pathology
chemical_list: D000978:Antiparkinson Agents; D004791:Enzyme Inhibitors; D007191:Indazoles; D007980:Levodopa; D016627:Oxidopamine; D019001:Nitric Oxide Synthase; C080122:7-nitroindazole; D004298:Dopamine